In automatic warewashing machines having a force-locking or force- and form-locking door lock which is disposed on the washing chamber side and may also be referred to as “pull-type release lock”, it is desirable to provide a unit which allows the door to be automatically opened by a few centimeters, either by the automatic warewashing machine in a cycle-dependent manner or by the user. Cycle-dependent opening is generally performed shortly before the end of the cycle to assist in the drying process. An automatic door opening system should always be made available to the user when there is no handle that would allow the user to pull the door open. This is the case, for example, in handle-free, fully integratable appliances.
A dishwasher having an automatic door-opening system is described, for example, in DE 10 2005 028 449 A1. In this appliance, the latching mechanism is mounted on the door and adapted to engage with a latch keeper secured on the washing chamber. In order to allow the door to be automatically opened to an ajar position in a program-controlled manner, the latch keeper is mounted to a closing plate which is movable by a motor. Upon receipt of a signal from the appliance controller, the motor extends the closing plate, and thus the latch keeper. In this manner, the door is opened to an ajar position, but kept in a latched state. In order to open the door, a handle is pulled up, thereby rotating a latching member to a position where it is no longer held by the latch keeper.
In document WO 2009/146 874 A1, too, the latch keeper mounted on the washing chamber is moved by a driving mechanism to open the door to an ajar position. Here, the driving mechanism is implemented as a spring which is tensioned as the door is opened further.
The aforementioned automatic door opening devices can only be used in automatic warewashing machines where the latching mechanism is mounted in the door and the latch keeper is disposed on the washing chamber or housing of the machine. This results in disadvantages.
For example, displays or controls cannot be mounted in the middle of the door, and the space actually available for such components is limited. It is necessary to use printed circuit boards which have cutouts for the latching mechanism and, therefore, are expensive to manufacture. In addition, in the case of door-mounted latching mechanisms, the door must have a cutout, which may lead to ingress of moisture and damage to the electronics.
U.S. Pat. No. 4,951,693 also describes a dishwasher having an automatic opening system. Here, a spring mechanism becomes loaded as the door is closed, and the door is latched in the closed position. Upon release of the latch by a solenoid, the spring mechanism automatically opens the door. Additional springs hold the door in a partially open position.
A spring mechanism for opening the door to an ajar position is also used in a dishwasher as described in EP 2 210 547 A1, where a pull-type release lock is used as the latching mechanism.
During operation, the washing chamber of automatic warewashing machines should be closed liquid-tight. To this end, the access opening of the washing chamber is surrounded by a seal against which the door presses. The latching mechanism must be capable of counteracting the force with which the seal presses against the door in the opening direction. If the latching mechanism is suddenly released, such as in U.S. Pat. No. 4,951,693 A, or is overcome by spring force (see EP 2 210 547 A1), then a sudden acceleration occurs. Door springs are provided to counteract this acceleration. However, such door springs may be misadjusted or may even break. In such case, the door drops down from the closed position to the horizontal and may injure persons as it drops. Small children present in the pivoting range of the door might even be struck dead.
German Patent Application No. DE 10 2008 058 257 A1 describes an automatic washing machine where the latching mechanism is mounted in the door. This automatic washing machine is also provided with a system for automatically opening the door to an ajar position. In this system, part of the latching mechanism is moved out of the body of the machine by a motor. The door remains latched until a release device is actuated.
DE 20 2007 006 818 U1, WO 2009/106 292 A1, EP 1 935 313 A1, which are incorporated by reference herein in their entireties, describe appliance doors openable by knocking on a decorative front panel of the door.